# Patent

## Title
Organic el display panel for reducing resistance of electrode lines

## Abstract

Method for fabricating an organic EL display panel having an EL region at every cross of first and second electrodes, including the steps of forming a plurality of first electrodes at regular intervals on a transparent substrate, forming an insulating layer in regions other than the EL regions, forming second supplementary electrodes on the insulating layer, forming an electric insulating barrier between adjacent EL regions perpendicular to the first electrodes, forming an organic EL layer in each of the EL regions with a shadow mask, depositing an electrode material on an entire surface inclusive of the organic EL layer, to form a plurality of second electrodes electrically connected to the second supplementary electrodes, and forming a protection film on an entire surface inclusive of the second electrodes.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a Divisional Application of prior U.S. patent application Ser. No. 11/703,251 filed Feb. 7, 2007, which is a Continuation Application of Ser. No. 10/654,896, filed Sep. 5, 2003, now U.S. Pat No. 7,211,947, which claims priority under 35 U.S.C. §119 to Korean Application Nos. P2002-53562 filed on Sep. 5, 2002, whose entire disclosures are hereby incorporated by reference.


BACKGROUND
1. Field
The present invention relates to display panels, and more particularly, to an organic EL display panel, and a method for fabricating the same.
2. Background
As a size of display becomes larger, demands on flat displays that occupies smaller spaces is increasing. As one of the flat displays, the organic EL display is paid attention. The organic EL display panel has advantages in that a thickness is thin, a matrix form of addressing is available, and a driving voltage is as low as below 15V.
There are a variety of full-color display methods in fabrication of the organic EL display panel, one of which that has the best luminance efficiency is a method employing a shadow mask. FIG. 1 illustrates a section showing a related art method for fabricating an organic EL display panel, and FIG. 2 illustrates a plan view of a shadow mask employed in FIG. 1.
Referring to FIGS. 1 and 2, in the related art method for fabricating an organic EL display panel, a transparent first electrode 2 is formed on a transparent substrate 1, a barrier (not shown) is formed thereon, and red, green, blue organic EL layer 3-1, 3-2, and 3-3 are formed in succession with a shadow mask 4 as shown in FIG. 2.
Then, second electrode material is deposited on an entire surface to form a second electrode in an EL region, thereby fabricating a full color organic EL display panel. The first electrode is an anode and a second electrode is a cathode.
However, the organic EL display panel fabricated thus has waste of power, and a consequential poor efficiency, caused by a resistance of the second electrode (cathode).
In order to overcome such a poor efficiency, though it is required that the second electrode line has a thickness greater than a certain value, it is difficult to fabricate a thickness greater than the certain value by the foregoing method.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an organic EL display panel, and a method for fabricating the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an organic EL display panel, and a method for fabricating the same, which can reduce resistances of electrode lines, to improve efficiency.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, the organic EL display panel having an EL region at a cross of each of first and second electrodes, includes an electric insulating barrier formed between adjacent second electrodes for electrical insulation of the second electrodes, and a supplementary electrode around each of the EL regions, the supplementary electrode being electrically connected to one of the second electrodes.
The second electrode and the supplementary electrode are electrically connected in the vicinity of an edge of the EL region.
The supplementary electrode is formed of a material selected from Cr, Al, Au, W, Cu, Ni, and Ag.
In another aspect of the present invention, there is provided an organic EL display panel including a substrate, first electrodes on the substrate, first supplementary electrodes electrically connected to sides of the first electrodes respectively, second electrodes perpendicular to the first electrodes, an organic EL layer at every cross of the first and second electrodes, second supplementary electrodes electrically connected to the second electrodes around the EL layers respectively, and an electric insulating barrier between adjacent second electrodes for electric insulation of the second electrodes.
In further aspect of the present invention, there is provided a method for fabricating an organic EL display panel having an EL region at every cross of first and second electrodes, including the steps of forming a plurality of first electrodes at regular intervals on a transparent substrate, forming an insulating layer in regions other than the EL regions, forming second supplementary electrodes on the insulating layer, forming an electric insulating barrier between adjacent EL regions perpendicular to the first electrodes, forming an organic EL layer in each of the EL regions with a shadow mask, depositing an electrode material on an entire surface inclusive of the organic EL layer, to form a plurality of second electrodes electrically connected to the second supplementary electrodes, and forming a protection film on an entire surface inclusive of the second electrodes.
The step of forming a plurality of first electrodes further includes the step of forming first supplementary electrodes electrically connected to sides of the first electrodes.
The second supplementary electrodes includes projected parts in the vicinity of edges of the EL regions so as to be in contact with the second electrodes, respectively.
It is to be understood that both the foregoing description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention claimed.



BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings;
FIG. 1 illustrates a section showing a related art method for fabricating an organic EL display panel;
FIG. 2 illustrates a plan view of a shadow mask employed in FIG. 1;
FIGS. 3A ̃3G illustrate perspective views each showing the steps of a method for fabricating an organic EL display panel in accordance with a preferred embodiment of the present invention;
FIGS. 4A ̃4G illustrate plan views each showing the steps of a method for fabricating an organic EL display panel in accordance with a preferred embodiment of the present invention;
FIG. 5A illustrates a section across a line I-I in FIG. 4G; and
FIG. 5B illustrates a section across a line II-II in FIG. 4G.



DETAILED DESCRIPTION
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. FIGS. 3A ̃3G illustrate perspective views each showing the steps of a method for fabricating an organic EL display panel in accordance with a preferred embodiment of the present invention, and FIGS. 4A ̃4G illustrate plan views each showing the steps of a method for fabricating an organic EL display panel in accordance with a preferred embodiment of the present invention.
Referring to FIGS. 3A and 4A, first electrodes 11 and pads 11-2 of second electrodes are formed of transparent material on a transparent substrate 10.
Then, referring to FIGS. 3B and 4B, for reducing resistance of the first electrodes 11, a first supplementary electrode 11-1 is formed such that a part of the first supplementary electrode 11-1 is overlapped with an edge of each of the first electrodes 11. The first supplementary electrode 11-1 is formed of a metal that has a resistance relatively lower than ITO of the first electrode 11, such as Cr, Al, Cu, W, Au, Ni, and Ag.
Referring to FIGS. 3C and 4C, an insulating layer 12 is formed in region except an EL region. The insulating layer 12 may be formed of any organic or inorganic material, as far as the material is insulator.
Referring to FIGS. 3D and 4D, a second supplementary electrodes 13 are formed on the insulating layer 12. Each of the second supplementary electrodes 13 has a projected part 13-1 in the vicinity of the edge of the EL region so as to be in contact with each of the second electrodes, electrically. The second supplementary electrode 13 to be in contact with each of the second electrodes is formed of a metal having a resistance lower than the second electrodes relatively, such as Cr, Al, Cu, W, Au, Ni, and Ag.
Referring to FIGS. 3E and 4E, a buffer layer (not shown) is formed between adjacent EL regions in a direction perpendicular to the first electrode 11, and an electric insulating barrier on each of the buffer layers.
Referring to FIGS. 3F and 4F, an organic EL layer 16 is formed in each of the EL regions with a shadow mask 15 having a plurality of via holes 15-1. The via holes 15-1 in the shadow mask 15 are in conformity with the EL regions.
Then, referring to FIGS. 3G and 4G, an electrode material is deposited on an entire surface inclusive of the organic EL layer, to form a plurality of second electrodes 17 electrically connected to the second supplementary electrodes 13, respectively.
Though not shown, a protection film is formed on an entire surface inclusive of the second electrode 17, and an encapsulation is carried out, to finish fabrication of the organic EL display panel. The first electrode is an anode and the second electrode is cathode.
FIG. 5A illustrates a section across a line I-I in FIG. 4G, and FIG. 5B illustrates a section across a line II-II in FIG. 4G.
Referring to FIGS. 5A and 5B, the organic EL display panel of the present invention has an EL region at every cross of the first electrodes 11 and the second electrodes 17.
Moreover, the electric insulating barrier 14, formed on each of the buffer layers 18 between adjacent EL regions, insulates the second electrodes 17 from each other, electrically.
Furthermore, the second supplementary electrode 13, formed around each of the EL regions, is connected to each of the second electrodes 17, electrically. Each of the second electrodes 17 is connected to one of the projected parts 13-1 of the second supplementary electrodes 13.
Thus, since the second supplementary electrode can reduce a resistance of the second electrode (cathode), an efficiency of the organic EL display can be improved, and a power required for operating the organic EL display can be reduced, to reduce waste of power.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

## Claims

1. A method for fabricating an organic EL display panel, comprising:
preparing a transparent substrate having a plurality of EL regions;
forming a plurality of first electrodes on the transparent substrate;
forming an insulating layer in regions other than the EL regions;
forming supplementary electrodes on the insulating layer;
forming an organic EL layer in each of the EL regions; and
depositing an electrode material on an entire surface inclusive of the organic EL layer, to form a plurality of second electrodes electrically connected to the supplementary electrodes, wherein each of the supplementary electrodes is formed around one or more of the EL regions and wherein contact areas between the second electrode and the supplementary electrodes are formed in corners of respective ones of the EL regions, the corners of respective ones of the EL regions projecting toward an interior area of respective ones of the EL regions.

2. The method as claimed in claim 1, wherein forming the plurality of first electrodes includes forming additional supplementary electrodes to be electrically connected to a portion of a respective one of the first electrodes.

3. The method as claimed in claim 1, wherein each of the supplementary electrodes is formed of a material selected from the group consisting of Cr, Al, Au, W, Cu, Ni, and Ag.

4. The method as claimed in claim 1, further comprising:
forming a protection film on an entire surface inclusive of the second electrodes.

5. A method for fabricating an organic EL display panel, comprising:
preparing a substrate having an EL region;
forming an anode on the EL region of the substrate;
forming a supplementary electrode coupled to the anode;
forming an organic EL layer on the anode; and
forming a cathode on the organic EL layer, wherein the supplementary electrode overlaps at least a portion of the anode, wherein the anode is arranged in a row direction of the substrate for connecting adjacent EL regions, wherein the supplementary electrode is arranged in a length direction of the anode, wherein the supplementary electrode is formed on and in direct contact with the anode, and wherein the EL region overlaps the anode but not the supplementary electrode.

6. The method as claimed in claim 5, wherein a lower part of the supplementary electrode is coupled to an upper part of the anode.

7. The method as claimed in claim 5, wherein the supplementary electrode has a width smaller than that of the anode.

8. The method as claimed in claim 5, wherein the supplementary electrode has resistance lower than that of the anode.

9. A method for fabricating an organic EL display panel, comprising:
preparing a substrate; and
forming a plurality of light emitting elements over the substrate, each light emitting element including a first electrode, an electroluminescent layer and a second electrode, the first electrode including a transparent electrode of indium tin oxide (ITO) and a supplementary electrode of Ag, wherein:
the supplementary electrode overlaps the transparent electrode,
the first electrode is an anode and the second electrode is a cathode,
the supplementary electrode is coupled to the transparent electrode,
the supplementary electrode is a single layer,
the supplementary electrode is formed on and in direct contact with the transparent electrode, and
the electroluminescent layer overlaps the transparent electrode but does not overlap the supplementary electrode.

10. The method as claimed in claim 9, wherein the cathode includes at least Ag.

11. The method as claimed in claim 9, further comprising:
forming an insulating barrier between adjacent light emitting elements.

12. The method as claimed in claim 9, further comprising:
forming a protection layer over the cathode.

13. The method as claimed in claim 9, further comprising:
encapsulating the organic EL display.

14. The method as claimed in claim 9, wherein the supplementary electrode has a smaller dimension than the first electrode.